This invention relates to additives for the electroplating of zinc. More particularly, it relates to polyamine brighteners for such electroplating.
The use of a variety of polyamines in various types of alkaline zinc plating is now common commercial practice, as reflected in the U.S. patents discussed below. Polyamines formed by the reaction of epichlorohydrin with ammonia or ethylenediamine are disclosed in Winters, U.S. Pat. No. 2,791,554 (1957). More recently, Rosenberg, U.S. Pat. No. 3,803,008 (1974), discloses polyamines from the reaction of epichlorohydrin with secondary and tertiary cyclic amines. Still more recently, Nobel et al., U.S. Pat. 3,869,358 (1975), and Duchene et al., U.S. Patents 3,871,974 and 3,886,054 (1975), disclose the use of quaternary polyamines formed by reacting epichlorohydrin with dimethylaminopropylamine and more preferably such polyamines further quaternized with alkyl halides and sulfates. The Duchene et al. polyamines include the uncrosslinked polyamines disclosed in an earlier patent to Greer, U.S. Patent 3,642,663 (1972), not connected with electroplating, and also use mercapto compounds. Similarly procedures detailed by Nobel et al. for the preparation of polyamines are essentially those of Greer. Nobel et al. also list triethanolamine as an example of an amine capable of forming a useful polyamine by condensation with epichlorohydrin.
However useful these compositions may be, it is desirable to have still better additives for zinc electroplating.